Regional Anesthesia - Clinical Tree

Synopsis

The use of ultrasound (US) has revolutionized regional anesthesia and become an important component of surgical anesthesia and acute pain management. Its relative safety and ease of performance make it a perfect option for surgeries in resource-poor settings. Specifically, regional anesthesia is used to desensitize a precise body part to painful stimulus. Research suggests that acute post-operative pain continues to be undertreated. US-guided regional anesthesia (UGRA) may be used to address acute post-operative pain and improve outcomes as well as provide surgical anesthesia for specific procedures. There are several applications for UGRA that are beyond the scope of this text. This chapter will focus on upper- and lower-extremity blocks. The overall purpose of this chapter is to provide step-by-step instruction on how to perform the most commonly used nerve blocks and to highlight their contribution in the context of reconstructive surgery in resource-poor settings.

Clinical Issues

Presentation

Acute post-operative pain is a recognized and challenging problem. UGRA is appropriate whenever post-operative pain control is a concern and can sometimes be used as the sole anesthetic, avoiding a general anesthesia altogether.

General Risks

The most worrisome risks for all peripheral nerve blocks include:

1.
Nerve injury
2.
Bleeding
3.
Infection

Associated Conditions

Patients with an existing nerve injury, or with skin or systemic infection (i.e., sepsis), or who have a coagulopathy of any etiology may not be good candidates for UGRA. The risks and benefits of a nerve block must always be considered.

Additional Considerations

Although this guide describes single-injection techniques, it is possible to place perineural catheters at the nerve targets to provide longer analgesia. Special equipment and pumps to provide continuous infusions are necessary and beyond the scope of this chapter.

Management

Choice of local anesthetic (LA): There are many acceptable LAs that can be used to meet specific patient needs. In general, LA can be classified by duration and depth of block. The most commonly used LAs and their concentrations are listed in Table 1.4.1 .

TABLE 1.4.1

Local Anesthetics and Their Concentrations

Local Anesthetic	Concentration
Local Anesthetic	Analgesic Block	Surgical Block
Short-Acting
Lidocaine	n/a	1.5%–2%
Mepivacaine	n/a	1.5%
Long-Acting
Ropivacaine	0.25%	0.5%
Bupivacaine	0.25%	0.5%

2.
Equipment:
- 1.
  US probe: High-frequency linear probe (10–15 MHz)
- 2.
  Needle: 100-mm insulated needle
  - a.
    There are several regional anesthesia needles commercially available that all share these qualities
- 3.
  An extension tube to attach a syringe of LA
- 4.
  Blunt tip to minimize risk of nerve or vascular injury
- 5.
  Skin preparation: chlorhexidine, Betadine, or alcohol
- 6.
  Probe cover: helpful to maintain strict aseptic technique. When using a probe cover, limit air bubbles from gel because they will distort the US image.
- 7.
  Monitors: pulse oximeter (audible heart rate tone), continuous ECG, and non-invasive blood pressure
- 8.
  Sedation: titrate to the needs of your patient. Nerve blocks can be performed with little or no sedation. Midazolam 2 mg, fentanyl 100 mcg, or propofol 20 to 50 mg are commonly used dosages.
3.
Preparation:
- 1.
  Position: ensure proper and comfortable patient positioning as well as ergonomic positioning of the US machine.
- 2.
  US image: obtain best US image of the target by adjusting depth, gain, focus, and frequency of the probe.
- 3.
  Skin preparation: strict aseptic technique is important at needle insertion site to minimize risk of infection.
- 4.
  Safety pause: immediately before performing block, confirm:
  - a.
    Correct patient
  - b.
    Correct surgery and side
  - c.
    Correct block and side
  - d.
    No contraindications to nerve block
  - e.
    All equipment including resuscitation equipment is available, including 20% lipid emulsion.
- 5.
  Injection technique:
  - a.
    An in-plane needle technique is described for all blocks included in this chapter, except for the ankle block.
  - b.
    Incremental injection of 5 mL with frequent aspiration for blood is important to minimize risk of complications.
  - c.
    High injection pressures may signify an intraneural injection, and redirection of the needle may be necessary.
  - d.
    Use slow injection of LA.

Techniques

I

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